Process for treating alkali wash liquors



Patented July 28, 1936 UNITED STATES PATENT OFFICE PROCESS FOR TREATING ALKALI WASH LIQUORS No Drawing. Application July is, 1934, Serial No. 135.011

7 Claim.

This invention relates to the treatment of alkaline wash liquors which have been employed in the refining of hydrocarbons.

In the refining of oils, aqueous solutions of 5 alkali, such as caustic soda, lime potassium hydroxide and sodium sulphide are used to wash the oils to remove hydrogen sulphide, and other acidic bodies such as phenols, thio-phenols, cresols, thio-cresols, and their higher homologues,

with the result that salts of the acidic bodies present in the oils treated are formed.

The object of my invention is to provide an improved process for recovering said organic acidic bodies from such alkaline wash liquors, and at the same time regenerate the said wash liquor.

In brief, my invention comprises extracting the acidic bodies from alkali wash liquors with a solvent for said acidic bodies which is substan- :0 tially immiscible with the alkali wash liquor.

In carrying out my process the solvent and the alkaline wash liquor are intimately contacted, then upon settling the alkaline wash liquor forms the lower layer and the solvent and acid bodies 5 form the upper layer. The wash liquor being practically freed of acidic bodies is returned to the system or run to storage for further use. The solvent and acidic bodies are then washed with approximately an equal volume of water and allowed to settle; the lower layer consists of water and the acidic bodies, and the upper layer the solvent free of acid bodies. The solvent is returned to the system or run to storage for further use. The water layer containing the acidic bodies" or rather salts of the acidic bodies", may be acidified to decompose said salts of the acidic bodies and free the acidic bodies, which then separate from the water layer. This phenolic layer is then separated from the water layer 40 and distilled to remove suspended water and impurities. The phenolic or cresolic distillate may be fractionally distilled to obtain fractions with a desired boiling range.

The step of washing the alcohol-phenolic layer 45 with water may be omitted. This layer may be distilled to separate the alcohol from the acidic bodies and distilled further with steam or vacuum to decompose the salts of acidic bodies and to recover the acidic bodies.

50 These salts, apparently are not very stable, as a result, the quantity of acidic bodies that a given amount of wash liquor, such as caustic soda, will hold in solution, depends upon the concentration of the caustic solution and the concentration of 55 the acidic bodies in the distillate being washed.

The quantity extracted increases directly with the concentrations. In treating certain cracked distillates, a 20 B. caustic solution will react with or absorb 15 to 20% by volume of acidic bodies from a distillate being washed which contains 5 approximately .05% of acidic bodies by volume. These saturated wash liquors will readily icse practically all the acidic bodies when washed with a relatively large quantity of hydrocarbon distillate free of acidic bodies. The lighter oils such as butane, propane and ethane are better solvents than the heavier oils.

Since the quantity of acidic bodies that the wash liquor will absorb increases with the alkalinity, it is usually desirable to use liquors with a high alkalinity for washing hydrocarbon fluids. The high salt content facilitates the subsequent extraction with alcohol, and permits longer use of the wash liquors before extraction or regeneration of same. The optimum concentration of sodium hydroxide in the wash liquor is between 20 and Heretofore, in refining cracked petroleum distillate the purpose of the alkaline wash liquor has been to remove hydrogen sulphide and no 25 attempt has been made to remove phenolic bodies from the distillate; the principal reasons bein that most distillates contained such a small amount of phenolic bodies and because there, was no economical method of recovering the phenolic bodies from the wash liquors. As stated above, the quantity of phenolic bodies that an alkaline wash liquor will absorb is not only a function of the concentration of the caustic in the wash liquor but also the concentration of the phenolic bodies in the hydrocarbon fluid being treated. For this reason the quantities of phenolic bodies in the wash liquor will vary from almost zero to 25%. If the wash liquor did contain 25% phenolic bodies it probably would not be economical to acidity the caustic solution to recover the phenolic bodies, but it could be recovered by my process.

The process, for example, can be carried out in the following manner:

One liter of caustic soda solution which has been employed to wash cracked gasoline and which contains phenolic bodies, is agitated with one liter of n-amyl alcohol in a separatory funnel for five minutes and allowed to settle; the caustic solution forming the lower layer is drawn oil, the remaining layer is the alcohol containing the phenolic salts. One quart of water is added to the alcohol in the separatory funnel and intimately contacted for two or three minutes and allowed to settle. The lower layer contains the water and phenolic salts. The upper layer contains the alcohol practically free of phenolic salts. The water layer containing the phenolic salts is drawn off and neutralized with acid. The phenolic bodies separate from and form a layer above the aqueous layer. The aqueous layer is practically free from phenolic bodies. If it is desired to recover the last traces of phenolic bodies from the neutralized aqueous solution, the same may be contacted with a solvent, such as a hydrocarbon, whose boiling point is either above or below that of the phenolic bodies, so that the phenolic bodies may be separated from the solvent by distillation. The phenolic bodies separated from the aqueous layer may be fractionally distilled to remove entrained water, impurities, and to obtain a product having a desired boiling range.

It may be necessary occasionally to redistill the alcoholic solvent to remove water and phenolic bodies.

Another way in which the process can be carried out is as follows:

One liter of caustic soda solution containing phenol c bodies is agitated with one liter of n-butyl alcohol in a separatory funnel for five minutes and allowed to settle; the caustic solution forming the lower layer is drawn off, the remaining layer is the alcohol containing the phenolic salts. About an equal volume of water is added to the alcoholic-phenolic bodies in the separatory funnel and int mately contacted for two or three minutes and allowed to settle into two layers. The lower layer contains the water and phenolic salts, and the upper layer contains the alcohol practically free of phenolic salts. The water layer containing the phenolic salts is drawn off and water is distilled off until the temperature of the residue reaches about 400 F. The residue is then steam distilled with superheated steam at 400 F. to decompose the phenolic salts and to recover them in the distillate. The phenolic distillate is then fractionally distilled if desired to obtain a product of desired end point.

In the batch process of contacting the alcohol and alkali wash liquor, the wash liquor instead of being contacted with an equal volume or more, may be contacted with two or more smaller portions of alcohol.

Alcohols or mixtures of same which are immiscible in the alkali wash liquors are suitable for extracting the phenolic compounds from same. Butyl, amyl and higher alcohols have been used successfully.

Solutions of low alkal nity may be used to wash hydrocarbon fluids to extract phenolic, cresolic and other acidic bodies, but it is desirable to use solutions of high alkalinity in the order of 10, 20, 30 B. or higher.

Some of the characteristics and properties of the phenolic bodies extracted from the gasoline fraction of cracked hydrocarbons are as follows:

Boiling range 3'70 to 410 F.

Specific gravity 1.04 at 20 C. Sulfur content by wt 3 to 10% Pour point Slightly soluble in water.

Soluble in paraflin hydrocarbons, alcohols, etc.

distillate may be added to the liquefied gas for example, butane, or the gas to be odorized may be contacted with the phenolic distillate.

The process described herein is not intended to be limited to the treatment of wash liquors which have been employed in treating petroleum oils, but wash liquors in other processes, whether they be used to wash gases or liquids.

I claim as my invention:

1. A process for treating alkaline wash liquorsl which have been employed in the refining of hydrocarbons and particularly the alkali wash liquors which have been employed in the treatment of cracked gasoline for the purpose of recovering phenolic bodies, which comprises, con- 1 tacting the alkali wash liquor with an amyl alcohol, separating therefrom, the alkali wash liquor for further use, washing the alcohol -phenolic layer with water, separating the alcohol layer for further use, acidifying the water-phenolic layer, 2 separating the phenolic layer, and fractionally distilling the phenolic layer to remove impurities therefrom.

2. A process for treating alkaline wash liquors which have been employed in the treatment of 2 hydrocarbon gases for the purpose of recovering organic acidic bodies which comprises, contacting the alkali wash liquor with an alcohol which is practically immiscible with said wash liquor, separating therefrom the alkali wash liquor for further use, washing the alcohol-organic acid layer with water, separating the alcohol layer for further use, acidifying the water organic acid layer, separating the organic acid layer, and fractionally distilling the organic acidic layer to re- 35 move suspended water.

3. A process for treating alkaline wash liquors which have been employed in the treatment of cracked hydrocarbon vapors or gases for the purpose of recovering phenolic bodies which comprises contacting the alkali wash liquor with n-amyl alcohol, separating therefrom the alkali wash liquor for further use, washing the alcoholic-phenolic layer with water, separating the alcohol layer for further use, acidifying the water-phenolic layer, separating the phenolic layer, and distilling the phenolic bodies to remove impurities.

4. A process for treating alkaline wash liquors which have been employed in the refining of hydrocarbons for the purpose of recovering organic acidic bodieswhich comprises, contacting the alkali wash liquor with an alcohol which is substantially immiscible with said wash liquor, separating therefrom the alkali wash liquor for further use, distilling the alcohol-organic acidic layer to recover alcohol, further distilling the residue, free from alcohol and containing the salts of the organic acidic bodies, with steam to decompose the said salts and to recover the organic 6 acidic bodies in the distillate.

5. A process for the production of phenolic compounds from the strongly alkaline aqueous wash liquors which have been used to wash petroleum distillates, which comprises contacting the with the phenolic compounds dissolved therein,

with water, separating the solvent layer from the water layer, and recovering phenolic compounds from the water layer.

6. A process for the production of phenolic compounds from the strongly alkaline aqueous wash liquors which have been used to wash petroleum distillates containing such compounds, which comprises contacting the said wash liquors with a solvent substantially immiscible therewith, the said solvent consisting of an alcohol of approximately four to five carbon atoms to dissolve phenolic compounds therein, separating the solvent layer from the wash liquor, and recovering phenolic compounds from the solvent 10 layer.

7. A process for the production of phenolic compounds from the strongly alkaline wash liquors which have been used to wash petroleum distillates, which comprises contacting the said wash liquors with an alcoholic liquid substantial- 1y immiscible therewith and thereby dissolving phenolic compounds in the said alcoholic liquid, separating the alcoholic liquid from the wash liquors, and recovering the phenolic compounds from the alcoholic liquid.

HARRY E. BRENNAN. 

